docs: async def help(self, timeout: DefaultNumType = _default) -> str:
          """
          Send the SMTP HELP command, which responds with help text.
  
          :raises SMTPResponseException: on unexpected server response code
          """
          await self._ehlo_or_helo_if_needed()
  
          async with self._command_lock:
              response = await self.execute_command(b"HELP", timeout=timeout)
          success_codes = (
              SMTPStatus.system_status_ok,
              SMTPStatus.help_message,
              SMTPStatus.completed,
          )
          if response.code not in success_codes:
              raise SMTPResponseException(response.code, response.message)
  
          return response.message